Other than those between our respective properties, Americans don't like fences. They just seem wrong. From somewhere I remember "Don't Fence Me In". Range wars were fought over fences in the 1800's. We demanded that "Mr. Gorbachov, tear down that wall!"
Now we appear to be at the edge of an existential crisis. Illegal immigrants, by the millions, crossing our southern border. The most obvious, efficient solution includes a fence; a really big fence. For many of us who realize just how ugly that is, it appears also to be an essential element of the solution.
Threats that "walls won't stop us" are silly and completely counterintuitive. As Charles Krauthammer points out, at the very least a wall will create "choke points" and will seriously slow the progress of the illegals.
It still doesn't feel right, does it? Just the way declaring war on another country doesn't feel right. But when you are left no choice you have to do it. That is where we are with illegal immigration. The governments of Central America and Mexico are so fraudulent and unrepentant that they are forcing us to abandon our liberal philosophies in favor of practicality in defending ourselves against an existential threat.
The illegals themselves are, in the view from down here, blameless. Just like the civilian, non-combatant populations and conscripted solidiers that are devastated in every war. They are being starved to death in their own countries and apparently encouraged (at least by the Mexican Government) by their governments to head North. Who wouldn't try it.
We seem to treat Mexico as though it is somehow entitled to special privileges. Maybe it is our collective guilt for having "stolen" part of their country. Perhaps it is our very American propensity to take pity on the impoverished. What we should be doing is sanctioning Mexico until it stops exporting its poorest citizens North.